褐飞虱翅型分化的分子机制

1、Two insulin receptors determine alternative wingmorphs in planthoppers,Hypothesis: wing morph determination in BPHs may be regulated by a nutrient-sensing pathway . The insulin/insulin-like growth factor (IGF) signalling (IIS) pathway is an evolutionarily conserved nutrient-sensing pathway thatmodul

2、ates growth and development in metazoans. BPHs have two insulin receptors, N.lugens(Nl)InR1 and NlInR2 . Knockdown of NlInR2 (dsNlInR2) led to a strong bias towards long-winged morphs compared to BPHs that were either not subjected to treatment(ck) or treated with double-stranded RNA(dsRNA) targetin

3、g the gene encoding green fluorescence protein (dsgfp) (Fig. 1c),Knockdown of NlInR2 (dsNlInR2) led to a strong bias towards long-winged morphs compared to BPHs that were either not subjected to treatment(ck) or treated with double-stranded RNA(dsRNA) targeting the gene encoding green fluorescence p

4、rotein (dsgfp) (Fig. 1c) knockdown of NlInR1 (dsNlInR1) produced the opposite response,inducing the development of short-winged BPHs(Fig. 1c) These findings indicate that expression of the two insulin receptors,NlInR1 and NlInR2, is tightly correlated with wing morph determination in BPHs, and that

5、they have fully opposite roles in the process.,Silencing of NlChico or NlAkt phenocopied dsNlInR1. By contrast, silencing of NlFoxo or NlPten phenocopieddsNlInR2 . NlLnk was probably irrelevant to wing morph determination, suggesting that NlLnk is either dispensable or functionally complemented by N

6、lChico. Next examined whether NlInR2 shares a common signalling cascade with NlInR1 .,Silencing of NlInR1, NlAkt or NlChico redirected development of dsNlInR2-treated BPHs from the long-winged to short-winged morphs (Fig. 2 a-e). Suppression of NlInR1NlPI(3)KNlAkt signalling is epistatic to the dsNl

7、InR2 effect .,DsNlInR2 but not dsNlInR1 strongly augmented the P-NlAkt level .,Given the high sequence similarity between NlInR1 and NlInR2, we then asked whether NlInR2 could physically interact withNlInR1 to form heterodimers. To this end, Flag-tagged NlInR1 (NlInR1Flag) was coexpressed with V5-ta

8、gged NlInR2 (NlInR2V5) in Drosophila S2 cells. The immunoprecipitation assay showed that NlInR2 was co-precipitated with NlInR1 (Fig. 2h), and that NlInR1NlInR1 homodimers had formed (Fig. 2i),Next asked whetherNlInR1 signalling regulates alternative wing morphs in an NlFoxo dependent manner. Double

9、-gene knockdown (dsNlInR1;dsNlFoxo)led to long-winged morphs . By contrast, dsNlInR1;dsgfp anddsNlInR2;dsNlFoxo produced short-winged BPHs and long-winged BPHs (Fig. 2j), respectively.,Next, we silenced insulin-like genes to identify the extracellular ligand(s)that triggers development of alternativ

10、e wing morphs in BPHs. DsNlIlp3 generated a significantly higherproportion of short-winged BPHs (Fig. 3a), and that the remaining threeNlIlp proteins had minor roles, if any, in wing morph switch .,Notably, tissue distribution analysis indicated that NlIlp3 was mainly produced in the brain (Fig.3c).

11、,whereas dsNlInR1 completely redirected the phenotypeof dsNlInR2, dsNlIlp3 only partially antagonized the effect of dsNlInR2 . Silencing of NlIlp3 in combination withthe remaining NlIlp genes did not synthetically enhance the dsNlIlp3 effect (Fig. 3e). DsNlFoxo could completelyreverse the effect of

12、dsNlIlp3 (Fig. 3f), suggesting that NlFoxo is the keyregulator downstream of NlIlp3,Finally, we found that the IIS pathway is a common regulatory mechanism for wing polyphenism in other members of the planthopper family . a, The wing morphs of S. furcifera planthoppers (SFPs). b, Knockdown of S. fur

13、cifera (Sf)InR1 resulted in the short-winged morph. c, The wing morphs of L. striatellus planthoppers (LSPs).d, Knockdown of L. striatellus (Ls)InR2 resulted in the long-winged morph.,The long-winged morph is the default developmental morph for planthoppers, which is dependent on NlInR1NlPI(3)KNlAkt

14、 signalling activity. However, in the wing buds, binding of NlInR2 to NlInR1 compromises NlInR1 signalling, which leads to the short-winged morph. NlIlp3 is the main upstream ligand that triggers long wing development. NlFoxo is the key downstream transcription regulator determining the wing morph by faithfully relaying NlInR1 signalling activity.,Important issues for future research,How environmental cues are translated into the molecular mechanism that regulates NlInR2 activity. precise mechanism by